Many types of input devices are available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch pads, touch screens, and the like. Touch sensitive devices, and touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch sensitive devices can include a touch sensor panel, which can be a clear panel with a touch sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel, or integrated with the panel, so that the touch sensitive surface can substantially cover the viewable area of the display device. Touch sensitive devices can generally allow a user to perform various functions by touching or hovering over the touch sensor panel using one or more fingers, a stylus or other object at a location often dictated by a user interface (UI) including virtual buttons, keys, bars, displays, and other elements, being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel or a hover event and the position of the hover event on the touch sensor panel, and the computing system can then interpret the touch or hover event in accordance with the display appearing at the time of the event, and thereafter can perform one or more operations based on the event.
Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object. More advanced touch screens are capable of detecting multiple touches simultaneously. In general, touch screens can recognize the position of the one or more touches on the touch sensor panel, and a computing system can then interpret the touches, either individually or as a single gesture in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
When a stylus has been used as an input device in a capacitive touch system, the stylus has traditionally been finger-like in nature. A conventional stylus is often simply a conductive rod with a finger-sized rounded tip large enough to disrupt the electric field lines between the drive and sense electrodes of a capacitive touch sensor panel. As such, conventional styluses are passive input devices in that they are incapable of actively transmitting stimulus signals or sensing a touch-induced capacitance change in a capacitive touch sensor panel.